Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D9/00—Stators
  • F01D9/02—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles
  • F01D9/04—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles forming ring or sector
  • F01D9/042—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles forming ring or sector fixing blades to stators
  • F01D9/044—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles forming ring or sector fixing blades to stators permanently, e.g. by welding, brazing, casting or the like
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D9/00—Stators
  • F01D9/02—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles
  • F01D9/04—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles forming ring or sector
  • F01D9/041—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles forming ring or sector using blades
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
  • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
  • F02C7/26—Starting; Ignition
  • F02C7/268—Starting drives for the rotor, acting directly on the rotor of the gas turbine to be started
  • F02C7/275—Mechanical drives
  • F02C7/277—Mechanical drives the starter being a separate turbine
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2220/00—Application
  • F05D2220/30—Application in turbines
  • F05D2220/32—Application in turbines in gas turbines
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2230/00—Manufacture
  • F05D2230/20—Manufacture essentially without removing material
  • F05D2230/21—Manufacture essentially without removing material by casting
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2300/00—Materials; Properties thereof
  • F05D2300/10—Metals, alloys or intermetallic compounds
  • F05D2300/13—Refractory metals, i.e. Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W
  • F05D2300/133—Titanium
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T50/00—Aeronautics or air transport
  • Y02T50/60—Efficient propulsion technologies, e.g. for aircraft

Definitions

• This invention relates generally to air turbine starters for gas turbine engines, and, in particular, to the air turbine stator inlet assembly used in such starters.
• the turbine starter 100 is joined to the jet turbine engine such that it travels with the jet.
• the weight of the turbine starter 100 is generally a calculated component of the overall weight of the aircraft and as such, reduces the total amount of cargo weight that the jet may transport.
• each additional pound of weight may cost the aircraft manufacturer a financial penalty.
• each additional savings of a pound may be credited to the manufacturer as a financial savings.
• the inlet assembly 103 is comprised of two components, namely the stator 121 and outer shell 123.
• the function of the stator fins 133 is to direct the supplied compressed air across the turbine blades.
• the narrowing passageways between the stator fins 133 act as nozzles to increase the velocity of the air as it strikes the rotating turbine blades 115.
• the outer shell 123 generally aligns the stator fins 133 to the turbine blades 115 and provides the outer portion of the contoured passage 135 leading to the air outlets 109.
• the outer shell 123 may be flared out or fabricated with additional sidewall thickness in the area accommodating the mating threads 121.
• the inlet assembly 103 weight as thickened may be greater than what could be achieved with a unitary inlet assembly.
• the outer shell 123 and stator 121 are fabricated from different metal alloys, the different relative hardness and thermal expansion and contraction properties may frustrate the threaded union and accelerate wear between the components.
• the invention provides an air turbine starter with an improved unitary inlet structure for gas turbine applications, and an associated improved unitary inlet structure.
• an air turbine starter having a main housing, a turbine assembly partially disposed within the main housing and a unitary inlet structure.
• the turbine assembly includes a turbine wheel having a plurality of circumferentially mounted blades.
• the unitary inlet structure is coupled to the main housing and substantially encloses at least a portion of the turbine wheel.
• the unitary inlet structure is characterized by a housing section having at least an inlet, an inner surface, and a mounting surface.
• a stator section is disposed at least partially within the housing section and has an outer surface. At least a portion of the housing section inner surface and at least a portion of the stator section outer surface form a flow path that fluidly couples the housing section air inlet to the turbine blades.
• the invention provides an air turbine starter unitary inlet structure.
• the unitary inlet structure is characterized by an annular housing having a longitudinal centerline. The housing defines an air inlet, an inner surface and a mounting surface.
• An annular air director is provided integrally formed as part of the annular housing, the annular air director disposed at least partially within the annular housing and having an outer surface.
• the oversized stator is disposed at least partially within the housing and has a plurality of angularly spaced, circumferentially mounted oversized stator fins connecting the stator to the annular housing.
• the oversized housing and stator are chemically milled to remove alloy from the oversized surfaces.
• the clearance between the chemically milled stator fins is measures and compared to one or more predetermined values.
• the chemical milling and measuring steps are repeated until at least the measured clearance between the chemically milled stator fins is substantially equal to one or more predetermined values.
• FIG. 1 A is a partial cross-sectional view of a prior art turbine starter with a two-piece stator inlet assembly
• FIG. 3 A is a half cutaway of the unitary inlet structure shown in FIG. 2;
• FIG. 3B is a partial cutaway of the unitary inlet structure shown in FIG. 2;
• FIG. 4 is a perspective view of the unitary inlet structure shown in FIGS. 3A and 3B;
• FIG. 6 is an interior view of the unitary inlet structure shown in FIG. 5;
• FIGS. 7A through 7C illustrate the steps of making the unitary inlet structure as shown in FIGS. 3A and 3B.
• the gearbox 111 is coupled to an output shaft (not shown), which is in turn coupled to, for example, a turbofan jet engine.
• the turbine assembly 107 includes a turbine wheel 113 with circumferentially mounted blades 115 and a rotatable drive shaft 117 that extends into the main housing 105 and is joined to gear 119 and gearbox 111.
• the unitary inlet and stator more simply identified as the unitary inlet structure 200 includes a housing section 204 with an interior surface 228 defining an air inlet 206, a mounting surface 208, and a flow path (represented by arrows 210) for conveying a flow of air therebetween.
• the housing 204 is an annular housing about a longitudinal centerline 212.
• Compressed air entering the inlet 206 is channeled by passage 222 through the stator 216, through the blades 115 of the turbine wheel 113, and to the outlet 202.
• the joining of the unitary inlet structure 200 to the main housing 105 may be accomplished by the any one of numerous forms of attachers such as, for example a threaded screw sockets 300 (see FIG. 3), set to receive bolts 224 extending from the main housing 105. Under appropriate circumstances, other suitable alternative joining methods may be employed.
• attaching bolts 224 and outlet vents 202 alternate in their placement about the exterior of the main housing 105. Under appropriate circumstances a bolt 224 may pass through a portion of the outlet 202, or the outlet 202 may provide access to the attaching bolt 224.
• FIGS. 3 through 6 The advantages of the unitary inlet structure 200 may be further appreciated with respect to the views provided in FIGS. 3 through 6.
• the perspective view of FIG. 4, along with the exterior view of FIG. 5 and interior view of FIG. 6 are provided to complement FIGS. 3 A and 3B.
• the housing 204 and stator 216 are advantageously formed as a unified whole. There are no threads, welds or other forms of attachment joining separately formed components as in the prior art.
• the term "unitary" as used herein with respect to the unitary inlet structure 200 is understood and appreciated to define the structure as an undivided whole, and not one assembled from a collection of separately manufactured parts.
• the central body 302 may be described as somewhat parabolic in shape such that the center-point 306 is extended towards the air inlet 206. More specifically, the central body 302 serves to assist in defining the flow path 210, directing the supplied compressed air into the stator fins 304. As shown in FIG 3 A, as the surface of the central body 302 expands from the center-point 306 to the stator fins 304, the defined passage 308 (the first part of flow path 202 shown in FIG. 2) narrows. This narrowing of the passage 308 serves to further compress and increase the air velocity as it is directed into the stator fins 304.
• the stator 216 may additionally include an outer ring 310.
• the outer ring 310 may encompass at least a portion of the distal edges 226 the turbine blades 115 (see FIG. 2). Improper placement of the stator 216 relative to the turbine blades 115 may result in inappropriate air flow between the stator and the turbine and correspondingly lower the turbine starter 100 performance.
• the stator fins 304 may have a cross-sectional shape of an air-foil 320 (see FIG. 3B).
• the leading edge 322 of each stator fin exists in a common plain 326 transverse to the longitudinal centerline 212.
• the trailing edge 324 of each stator fin exists in a common plain parallel to the plain defined by the plurality of leading edges 322.
• the unitary inlet structure 200 may include a flanged skirt 312 or other suitable structure to which a supply hose may readily be attached.
• the non- moving, rigidly mounted stator fins 304 serve in part to shelter the turbine assembly 107 from the direct brunt of the potentially non-uniform thrust force provided by the compressed air as it exits the supply hose and enters the air inlet 206.
• the compressed air is directed by the passage 308 to arrive at the stator fins 304 with an alignment of flow that is substantially parallel to the longitudinal centerline 212.
• the stator fins 304 are oriented with an angle of attack to uniformly align the flow of air for delivery into the turbine blades 115. It is understood and appreciated that an angle of attack of an, such as one of the turbine blades 115, is the angle at which the relative wind meets the airfoil. In at least one embodiment, the angle of attack is about 36.738 degrees. Further, in at least one embodiment the angular spacing of the stator fins 304 may be symmetric. [0040] As noted above, prior art turbine starters have been found to experience occasional mouse bites to the turbine blades 115.
• the harmonics created by the air passing from the stator 216 through the turbine blades 115 which create the environment for mouse bites to occur may be substantially prevented.
• the angular spacing of the stator fins 304 is asymmetric. The asymmetric spacing of the stator fins 304 induces different portions of the stator 216 to deliver air to the turbine blades 115 slightly differently.
• the asymmetric angular spacing of the stator fins 304 may be more fully appreciated with reference to FIG. 6.
• the stator fins 304 may be subdivided into at least three groups.
• the first group 600 of stator fins 304 may be characterized by substantially equal angular spacing 602 for about the total number of overall stator fins plus at least one, the spaced arrangement forming a first arc 604 having a first end 606 and a second end 608.
• the second group 610 of stator fins 304 may be characterize by substantially equal angular spacing 612 for about the total number of overall stator fins minus at least one, the spaced arrangement forming a second arc 614 having a first end 616 and a second end 618.
• one half of the transition group 620 is placed between the second end 608 of the first arc 604 and the first end 616 of the second arc 614.
• the second half of the transition group 620 is placed between the second end 618 of the second arc 614 and the first end 606 of the first arc 604.
• the stator 216 comprises 29 stator fins 304.
• the number of stator fins 304 in each of the above described groups may be as follows; the first group 600 consisting of 14; the second group consisting of 13; and the transition group consisting of 2.
• the angular spacing 602 of the fins of the first group 600 (stator fins 304 1 through 14) is about 12.0000 degrees.
• the angular spacing 612 of the fins of the second group 608 (stator fins 304 16 through 28) is about 12.8571 degrees.
• the angular spacing 622 of the transition group 622 (stator fins 304 15 and 29) is about 12.4286 degrees.
• angular spacing is to be understood and appreciated to imply angular increments about the circumference of a circle. For example, placing 12 points at the angular spacing of 30 degrees along the circumference of a circle will provide the hour marks as are commonly seen on traditional non-digital clocks. Moreover, as measured from a consistent point, one stator fin to the next (leading edge 322, trailing edge 324 or other reference point), if stator fin A' is to be angularly spaced 12.0000 degrees from stator fin A, the leading edge 322 of stator fin A' will be 12.0000 degrees from the leading edge 322 of stator fin A.
• the titanium alloy may be significantly lighter than prior art stator and inlet assemblies wherein the housing is fabricated in titanium alloy, but the stator is fabricated from a heavier alloy such as a common inconel alloy.
• the unitary inlet structure 200 may be about 0.5 pounds lighter than conventional prior art inlet and stator assemblies, an achievement that may translate to a savings of about $500 per takeoff to the aircraft operator.
• FIG. 7 a preferred method of fabricating a titanium unitary inlet structure 200 will now be described as is illustrated in FIG. 7. It will be appreciated that the described method need not be performed in the order in which it is herein described, but that this description is merely exemplary of one preferred method of fabricating a titanium unitary inlet structure 200 in accordance with the present invention.
• fabrication involving casting may be used. With the use of casting there is no requirement that the stator 216, and more specifically the stator fins 304 be separately manufactured, arranged and joined by an appropriate process. Casting advantageously permits the outer housing 204 and internal stator 216 to be formed of substantially the same alloy and at substantially the same time.
• an oversized annular housing 704 having a longitudinal centerline 712 is cast.
• the oversized housing defines an air inlet 706, a mounting surface 708 and a flow path therebetween.
• Inside the housing 704 is integrally cast an oversized stator between the air inlet 706 and mounting surface 708, substantially transverse to and concentric with the longitudinal centerline 712.
• the internal cast stator is further characterized by a central circular body with a plurality of angularly spaced circumferentially mounted oversized stator fins 752 connecting the stator to the housing 704.
• the titanium alloy used in the casting is commonly known and identified as Ti6A14V.
• the angular spacing of the stator fins may be symmetrical. In at least one alternative embodiment the angular spacing of the stator fins may be asymmetrical, as described above.
• oversized refers to casting the unitary inlet structure 750 with excess thicknesses relative to the design specifications. It is to be further understood and appreciated that substantially all of the components are uniformly oversized. For example, if the cast stator fins 752 are oversized by about 2 millimeters in thickness, then so too is the cast housing 704 oversized by about 2 millimeters in thickness. As shown in FIG. 7A the clearance 754 between the freshly cast stator fins 752 may be small, and below design specifications.
• the cast oversized unitary inlet structure 750 are placed in a chemical bath 756. More specifically the oversized unitary inlet structure 750 may be suspended in a milling tank 758 containing an appropriate chemical milling solution 760 for the titanium alloy used in the casting. Under appropriate circumstances it may be desired to pre-clean the oversized unitary inlet structure 750 to remove foreign materials such as oil, etc. Generally speaking, agitation of the milling solution 760 may occur during the chemical milling process to improve exposure of the surfaces to the milling solution 760 as well as to maintain a balanced concentration of the milling solution 760 throughout the tank 758.
• the duration of the chemical milling process may be determined by calculating the rate of alloy removal for the chemical milling agent employed. Due to the precise clearance between the stator fins set forth in the design specifications, it may be desirable to calculate a first duration sufficient to remove substantially about 50 to 90 percent of the oversizing alloy. Upon removal from the chemical bath 756, the technician may measure the clearance 762 between the chemically milled stator fins 764 of the chemically milled unitary inlet structure 766 and compare the measured clearances to the design specifications providing one or more predetermined values.
• the rate of removal may be recalculated and used to determine the duration for a repeat of the chemical milling process, if necessary, sufficient to provide clearance between the stator fins within design specifications.
• the process of chemical milling may be repeated three times, the first removing substantially about 50% of the oversizing alloy, the second removing about 90% of the remaining oversizing alloy, and the third removing substantially all of the remaining oversizing alloy to provide clearance 764 within design specifications.
• the stator fins are chemically milled until at least the measured clearance between the chemically milled stator fins is substantially equal to one or more of the predetermined values set forth in the design specifications.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

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• 2004
  • 2004-09-09 WO PCT/US2004/029412 patent/WO2005042948A2/en active IP Right Grant
  • 2004-09-09 DE DE602004003969T patent/DE602004003969T2/de active Active
  • 2004-09-09 EP EP04816851A patent/EP1664506B1/de not_active Expired - Fee Related

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